Method for preparing lithium iron phosphate nanopowder

Patent metadata

Field	Value
Publication number	US-9608270-B2
Application number	US-201414429066-A
Country	US
Kind code	B2
Filing date	Jan 9, 2014
Priority date	Jan 10, 2013
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

The present invention relates to a method for preparing a lithium iron phosphate nanopowder, including the steps of (a) preparing a mixture solution by adding a lithium precursor, an iron precursor and a phosphorus precursor in a reaction solvent, and (b) putting the mixture solution into a reactor and heating to prepare the lithium iron phosphate nanopowder under pressure conditions of 1 to 10 bar, and a lithium iron phosphate nanopowder prepared by the method. When compared to a common hydrothermal synthesis method, a supercritical hydrothermal synthesis method and a glycothermal synthesis method, a reaction may be performed under a relatively lower pressure. Thus, a high temperature/high pressure reactor is not necessary and process safety and economic feasibility may be secured. In addition, a lithium iron phosphate nanopowder having uniform particle size and effectively controlled particle size distribution may be easily prepared.

First claim

What is claimed is:

1. A method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery, comprising the steps of:
(a) preparing a mixture solution by adding a lithium precursor, an iron precursor and a phosphorus precursor in a reaction solvent; and
(b) putting the mixture solution into a reactor and heating to prepare the lithium iron phosphate nanopowder under pressure conditions of 1 bar or more to less than 10 bar,
wherein the reaction solvent is at least one selected from the group consisting of 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, and an isomer thereof.

2. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 1 , further comprising the step of (c) heat treating the lithium iron phosphate nanopowder thus prepared to form a coating layer at a portion or a whole of a surface of an individual particle of the nanopowder.

3. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 2 , wherein the heat treating is performed by heating to a temperature range of 400 to 900° C.

4. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 1 , wherein the lithium iron phosphate nanopowder prepared in Step (b) is sequentially conducted a washing step and a drying step.

5. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 4 , wherein the washing step is performed by sequentially using acetone and methanol.

6. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 4 , wherein the drying is performed at 20 to 160° C. for 2 to 40 hours.

7. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 1 , wherein the step (b) is performed at a temperature less than or equal to a boiling point of the reaction solvent.

8. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 1 , wherein Step (b) is performed at a temperature range of 150 to 235° C.

9. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 1 , wherein Step (b) is performed for 1 to 72 hours.

10. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 1 , wherein the lithium precursor is at least one selected from the group consisting of lithium acetate dihydrate (CH 3 COOLi.2H 2 O), lithium hydroxide monohydrate (LiOH.H 2 O), lithium hydroxide (LiOH), lithium carbonate (Li 2 CO 3 ), lithium phosphate (Li 3 PO 4 ), lithium phosphate dodecahydrate (Li 3 PO 4 .12H 2 O) and lithium oxalate (Li 2 C 2 O 4 ), and a mixture thereof.

11. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 1 , wherein the iron precursor is at least one selected from the group consisting of iron citrate (FeC 6 H 5 O 7 ), iron citrate hydrate (FeC 6 H 5 O 7 .nH 2 O), ferrous sulfate heptahydrate (FeSO 4 .7H 2 O), iron(II) oxalate dihydrate (FeC 2 O 4 .2H 2 O), iron acetyl acetonate (Fe(C 5 H 7 O 2 ) 3 ), iron phosphate dihydrate (FePO 4 .2H 2 O) and ferric hydroxide (FeO(OH)), and a mixture thereof.

12. The method for preparing a lithium iron phosphate nanopowder for a lithium secondary battery of claim 1 , wherein the phosphorus precursor is at least one selected from the group consisting of tri-ammonium phosphate trihydrate ((NH 4 ) 3 PO 4 .3H 2 O), ammonium phosphate ((NH 4 ) 2 HPO 4 ), ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) and phosphoric acid (H 3 PO 4 ), and a mixture thereof.

Assignees

• Lg Chemical Ltd

Inventors

• Jun In Kook
• Cho Seung Beom
• Oh Myoung Hwan

Classifications

• H01M4/136

  Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy · CPC title

• C01P2002/30

  Three-dimensional structures · CPC title

• H01M4/625

  Carbon or graphite · CPC title

• H01M10/052

  Li-accumulators · CPC title

• C01B25/45

  containing plural metal, or metal and ammonium · CPC title